An engine of a vehicle generating an actual driving force generates a large amount of heat energy during a process of converting chemical energy into kinetic energy. When heat energy is excessively generated, the engine and/or parts around the engine are overheated and are thus damaged or destroyed, which may lead to various problems such as big breakdowns and accidents and greatly reduce efficiency of the engine itself, etc. Therefore, to remove the problems, a vehicle is generally equipped with an apparatus for cooling the engine. A representative method used to cool the engine is a method for using cooling water and includes a radiator distributing cooling water to a circumference of the engine and cooling the cooling water to absorb heat generated from the engine and then emits the absorbed heat from the radiator, thereby preventing the engine from being overheated. Further, an apparatus for cooling the interior of room for comfort of a vehicle driver and passengers is also provided. A heat exchanger like a condenser for cooling a refrigerant of an air conditioner for cooling the interior of room has been used.
The heat exchangers such as the radiator and the condenser as described above are provided in front of an engine room of the vehicle and the heat exchangers exchange heat between air therearound and a heat exchange medium inside the heat exchanger. In this case, to increase heat radiation efficiency of the heat exchanger, an axial-flow fan that may forcibly ventilate air to the heat exchanger is provided.
The axial-flow fan is generally accommodated in a shroud, a motor, etc., for rotating the axial-flow fan is fixed to the shroud, and the shroud is mounted to fix its position. As such, an axial-flow fan assembly configured of the axial-flow fan, the shroud, the motor, etc., is mounted in the heat exchanger or a floor of the engine room to be disposed in front of or in back of the heat exchanger.
As illustrated in FIG. 1, an assembly of the fan shroud according to the related art is greatly configured of a fan 10 and a shroud 20. The fan 10 is configured to include a hub coupled with a rotating shaft of a motor 11, a plurality of blades 12 formed on an outer circumferential surface of the hub at a predetermined interval, and J-letter or hook-shaped bands connecting end portions of the blades 12.
The shroud 20 is formed along an outermost rotating trajectory of the blade 12 in a shape enclosing the blade 12 not to be in contact with the band and thus is adjacent to the heat exchanger (not illustrated).
An end portion of the shroud 20 corresponding to an opposite side adjacent to the heat exchanger is integrally formed with a bell mouth 21 curved at a constant curvature and the motor 11 of which the rotating shaft is coupled with the hub is fixedly mounted by a separate motor mounting part 22.
Further, the shroud 20 is provided with a plurality of stators 23 connecting an outer side surface of the motor mounting part 22 to an outer side surface of the bell mouth 21.
According to the related art configured as described above, as the blade 12 of the fan 10 rotates by receiving a driving force of the motor 11, air passing through the heat exchanger is forcibly sucked such that most air passes through the blade 12 as it is and the rest air flows to the bell mouth 21 along an inner side surface of the shroud 20, and the air flowing to the bell mouth 21 is discharged to an outside of the fan 10.
In this case, however, a portion adjacent to the bell mouth 21 is an end portion in which air delivered by the fan 10 flows and an air flow is suddenly changed at the portion of the bell mouth 21 to easily form a swirling airflow, thereby causing noises.
Korean Patent No. 0729650 (Registered on Jun. 12, 2007: Shroud Having Structure For Noise Reduction, hereinafter, referred to as Related Art Document) discloses a shroud having a structure for noise reduction in which a ventilating part into which an axial-flow fan is inserted is arranged with a swirling airflow-preventing saw-teeth inclined in a rotating direction of the axial-flow fan to suppress a swirling airflow and a recirculating airflow from occurring upon air ventilation due to a rotation of the axial-flow fan, thereby effectively reducing noises and ventilating air. As described in the Related Art Document, the shroud to which the swirling airflow-preventing saw-teeth is applied is illustrated in FIG. 2.
By the way, as illustrated in FIG. 2, in the fan shroud assembly for a vehicle, a shroud 20 does not generally have a symmetric shape and a portion where a space between the bell mouth 21 provided with the swirling airflow-preventing saw-teeth and an outer edge of the shroud is narrow due to space constraints when the shroud is equipped in the vehicle is formed in areas adjacent to upper ends and lower ends of the bell mouth and the ventilating part.
The change in flow pressure is rather increased at the portion due to the swirling airflow-preventing saw-teeth 24 formed to prevent noises, thereby increasing the occurrence of noises.